We present a method for interactive computation of indirect illumination in large and fully dynamic scenes based on approximate visibility queries. While the high-frequency nature of direct lighting requires accurate visibility, indirect illumination mostly consists of smooth gradations, which tend to mask errors due to incorrect visibility. We exploit this by approximating visibility for indirect illumination with imperfect shadow maps ---low-resolution shadow maps rendered from a crude point-based representation of the scene. These are used in conjunction with a global illumination algorithm based on virtual point lights enabling indirect illumination of dynamic scenes at real-time frame rates. We demonstrate that imperfect shadow maps are a valid approximation to visibility, which makes the simulation of global illumination an order of magnitude faster than using accurate visibility.

Figure 1: We generalize screen-space ambient occlusion (SSAO) to directional occlusion (SSDO) and one additional diffuse indirect bounce of light. This scene contains 537k polygons and runs at 20.4 fps at 1600×1200 pixels. Both geometry and lighting can be fully dynamic. AbstractPhysically plausible illumination at real-time framerates is often achieved using approximations. One popular example is ambient occlusion (AO), for which very simple and efficient implementations are used extensively in production. Recent methods approximate AO between nearby geometry in screen space (SSAO). The key observation described in this paper is, that screen-space occlusion methods can be used to compute many more types of effects than just occlusion, such as directional shadows and indirect color bleeding. The proposed generalization has only a small overhead compared to classic SSAO, approximates direct and one-bounce light transport in screen space, can be combined with other methods that simulate transport for macro structures and is visually equivalent to SSAO in the worst case without introducing new artifacts. Since our method works in screen space, it does not depend on the geometric complexity. Plausible directional occlusion and indirect lighting effects can be displayed for large and fully dynamic scenes at real-time frame rates.

Figure 1: Our method computes global illumination by rasterizing many thousands of tiny micro-buffers (middle left) in parallel, using a sub-linear point rendering technique with an importance-warped projection. Two interior levels of the hierarchy with 1M points are shown on the left. The middle image renders at 1.1 Hz (512 × 512 res.). The right scene (700K triangles converted to 1M points) renders at 0.7 Hz. AbstractRecent approaches to global illumination for dynamic scenes achieve interactive frame rates by using coarse approximations to geometry, lighting, or both, which limits scene complexity and rendering quality. High-quality global illumination renderings of complex scenes are still limited to methods based on ray tracing. While conceptually simple, these techniques are computationally expensive. We present an efficient and scalable method to compute global illumination solutions at interactive rates for complex and dynamic scenes. Our method is based on parallel final gathering running entirely on the GPU. At each final gathering location we perform micro-rendering: we traverse and rasterize a hierarchical point-based scene representation into an importance-warped microbuffer, which allows for BRDF importance sampling. The final reflected radiance is computed at each gathering location using the micro-buffers and is then stored in image-space. We can trade quality for speed by reducing the sampling rate of the gathering locations in conjunction with bilateral upsampling. We demonstrate the applicability of our method to interactive global illumination, the simulation of multiple indirect bounces, and to final gathering from photon maps.

The interaction of light and matter in the world surrounding us is of striking complexity and beauty. Since the very beginning of computer graphics, adequate modelling of these processes and efficient computation is an intensively studied research topic and still not a solved problem. The inherent complexity stems from the underlying physical processes as well as the global nature of the interactions that let light travel within a scene. This paper reviews the state of the art in interactive global illumination (GI) computation, i.e., methods that generate an image of a virtual scene in less than 1 s with an as exact as possible, or plausible, solution to the light transport. Additionally, the theoretical background and attempts to classify the broad field of methods are described. The strengths and weaknesses of different approaches, when applied to the different visual phenomena, arising from light interaction are compared and discussed. Finally, the paper concludes by highlighting design patterns for interactive GI and a list of open problems.

Figure 1: Using voxel-based visibility (center), we are able to display real-time near-field illumination with directional occlusion (left, 25 fps) and interactive global illumination (right, 4.9 fps). The indirect light is exaggerated for visualization. AbstractComputing a global illumination solution in real-time is still an open problem. We introduce Voxel-based Global Illumination (VGI), a scalable technique that ranges from real-time near-field illumination to interactive global illumination solutions. To obtain a voxelized scene representation, we introduce a new atlas-based boundary voxelization algorithm and an extension to a fast rayvoxel intersection test. Similar to screen-space illumination methods, VGI is independent of the scene complexity. Using voxels for indirect visibility enables real-time near-field illumination without the screen-space artifacts of alternative methods. Furthermore, VGI can be extended to interactive, multi-bounce global illumination solutions like path tracing and instant radiosity.